The Aqua MODIS and SeaWiFS Level-3 9 km merged chlorophyll products are generated routinely for daily, 8-day, monthly, seasonal and annual time periods once the refined products for each of the contributing missions are processed. Increased coverage over the single mission product is realized through the merging of the two data sets. There is a substantial improvement (> 50%) in coverage at the daily level, decreasing with the increase in the temporal period binned.

The MODIS/SeaWiFS merged product is generated in essentially two steps. First, the MODIS Level-3 file is reduced in resolution from 4 to 9 km to match the global resolution of the SeaWiFS chlorophyll product. This involves combining the sum and sum squared field values for the (typically) four 4 km bins into the corresponding single 9 km bin. In the second step, the reduced-resolution MODIS file and the corresponding SeaWiFS Level-3 file are combined. Because both input files are at the same 9 km resolution, the summing is performed bin-by-bin. The Standard Mapped Image file that is generated from the merged Level-3 binned file stores scaled 16 bit integer values rather than the usual 8 bit values, giving the user much greater numerical precision. The actual images displayed on the Ocean Color website in PNG format are provided for visual inspection only.